Method of grinding workpieces



1935- c. BOOTH ET! AL 2,004,649 I METHOD OF GRINDING WORKPIECES Filed May 19, 1950 ll; 2 ll 3 'Jlz 4 lz j jijf J3 J5 QILQ auww,

Patented June 11, 193% METHOD OF- GRINDING womrrrscns Clement Booth and Sol Einstein,

Cincinnati,

Ohio, assignors, by mesne assignments, to The Heald Machine Company, Worcester, corporation of Massachusetts Mass., at

Application May 19, 1980, Serial No. 453,540 I 3 Claims. (01.51-278) This invention relates to improvements in grinding and has particular reference to an improved process for production of tubular articles slush as the bearing rings or races for ball bears. Prior to the present invention, it has been customary practice in the production-of articles such as inner rings or races for ball bearings, and like articles, to mount the work piece in a suitable rotating chuck, .or the like, and to grind inner or seating face to the desired cylindrical form which might or might not be concentric with the general outer surface of the work piece depending on the accuracy of the chuck members. These inaccuracies are normally of such work piece be slightly incorrect as to size it is commercially impossible to replace the same in the chuck for regrinding in a position degree that if a which would be concentric with that initially cupied. Thus, unless the work piece be suitably undersize, it is impossible to regrind to a true circle not having high and low spots.

This grinding of the inner surface of the race ring having been performed, the standard practice involves mounting the article on a suitable holder or mandrel, and rotating the same while so mounted in opposition to a grinding wheel generating the ball seat or race way in the outer face. The concentricity of the race way with the inner ground seat, operative to determine the sition of the bearing as a whole when in use, is

therefore dependent on the interfitting of rin mercial basis.

Due to the fact that the ungrooved portions of the outer surface of the inner ring are a nonfunctioning surface as respects the bearingwhen in use, no particular attention has been given to this surface.

process in which either the inner surface or outer race way for example may be accurately, correctively reground, if the inner surface be and mandrel, on the mounting of the mandrel itself as to concentricity, and in addition on any looseness or play of supporting portions of the machine in engagement with the mandrel. As a result, accurate production of these parts, to within the desired fraction of a thousandth of an inch, these limitations being desirable in machiningoperations of the present day, has vbeen extremely difficult, if not impossible on acomconcentricity willbe accurately maintained both during the original grindingand during any subsequent corrective actions'thereon. v v A further object of the'invention is themethe the interdependence of the inner and outer operative surfaces of the work piece and will provide a common position determinator for the work piece during production of both of saidsurfaces.

An additional object isthe provision of a process for production of work pieces of the character above set forth, of maximum accuracycapable of interchangeable employment, and which, will be effective to eliminate the dependence of the work pieces for accuracy on adjustment and engagementof chucks and centers, or general spring or play in'the supporting portion of the. grinding machine. p p

' According to the present invention, the process is carried out by supporting rotationon a preformed cylindrical surface of the tated onsaid preformed surface and simultaneouslyor subsequently producing one .or more additional surfaces on said workpiece while the latter is supported for rotation on the same prefor DO- faces produced is concentric to the preformed surface and accordingly the surfaces produced are concentric to each other. By this arrangement, the plurality of concentric surfaces'maybe produced while the workpiece is mounted ina single supporting member or each surface may be produced by mounting ofthe workpiece in, separate supporting members. Since the workpiece, however, is rotated on a preformed cylindrical surface during the cutting of each of the plurality of concentric surfaces, the surfaces produced will be entirely concentric. i s

. To facilitate an understanding of the process in question a series of diagrams thereof are illustrated in the appended drawing. n which the way ball bearing.-

Figure 2 is an end view of a work piece prior to grinding the surface, inequalities being shown in exaggerated 'form for ease of the subsequent views. I

Figure 3 is a similar view of the workpiece after the first operation has been performed thereon. Figure 4 is a similar view of'the workpiece fter another operation has been performed thereon.

S PATENT "OFFICE-'3,

undersize or the outer surface oversize, and true vision of an improved process which will eliminate the. workpiece for said workpiece and producing a surface on said workpiece while the latter is supported and roformed surface. In this manner, each ofthesur- Figure 1 is a sectional view ofa double race comparison with Figure 5 is a similar view of the completed workpiece.

Figure 6 is a diagrammatic view, in elevation, to bring out the manner of performance of the first step in the process.

Figures 7 and 8 are diagrammatic views, re-

' spectively in elevation and in plan showing the in the finished article becomes a' finished surface l3a, adapted for tight fitting engagement with a shaft l5, for example, while the outer surface I! is intended to be provided with therace ways as at l6 and IT, for example,to receive the balls l8 of the complete bearing structure. It is essential in the finished article, that the race ways l6 and I1 bereduced to precisely the correct diameter or, size and also that they be precisely concentric to the surface I 3a, and thus, in turn, concentric to the axis of revolution of shaft I5 to eliminate eccentric or gyratory movementof the shaft and consequent vibration when the bearing is put into operation. l Itwill be noted by reference to Figure 1 that the outer surface l2 of the inner ring ID has no functional purpose as a surface, there'being a suitable clearance between it and the inner surface of the outer bearing ring l9. Consequently in the past, no particular attention has been given to the manner in which this surface was machined or finished and no attempt made to establish any definite relationship between. said surface and theoperative faces of the bearing ring.

In the present process of manufacture, the first step consists in the initial formation of a definite cylindrical outer surface on the member 10, preferably by precision grinding on a centerless grinder, asshown in Fig. 6, to the end that the work piece will be a true circle in cross section and 'round within a fractional thousandth of an inch.

Obviously, the first step may be eliminated when the workpiece is provided with a preformed surface of revolution whichis concentric to the .desired surfaces to be produced-onthe workpiece.

' After this outer surface has been properly formed, said surface is used as the position determinate for the work during the formation of a multiplicity of surfaces concentric thereto; in the construction shown, these surfaces comprise-the surface of the workpiece resting on a suitable support such as a work rest blade 20, and at the same time in engagement with a second. throat forming member which mayv assume, for example, the form of a driven friction disc or regu1ating wheel 2|, the use of chucks, or like holding members, is eliminated. This is a pronounced advantage, since, as 'abovestated, it is found impossible in commercial chuckskafterf having withdrawn 9. piece which has been internally ground, to reinsert the piece in the same or another chuck and just spark out the interior with the grinding wheel, due ,to the fact that there will be .a slight difference. in the-orbit or path of the movement of the piece when rechucked, so that it will not revolve about the identical axis on which its surface was previously produced. While this variation may be of the nature of a thousandth of an inch displacement of the ads, or even less, when considered as an error in diameter it is several times the allowable commercial limit of error in production, and of a degree suflicient to seriously impair the accuracy -and life of the bearing, and the piece if reground in this manner from slightlyundersize 'when completed, to the newly determined circle will generally be appreciably oversize. 1

The process contemplates the utilization'of the surface I? in the manner above pointed out during the formation of the central aperture or seat l3a by a grinding operation, as indicated in Figs. 7 and 8, said surface being. produced while the Workpiece'is supported androtated on the first or preformed surface l2. Obviously,by such rotation of the workpiece as the surface I3a'is formed, .said surface, is concentric tothe surfac'elZ. I

Likewise, the process contemplates the corresponding' utilization of a work rest member 20a anda positioning member 2la for engagement with the preformed'periphery I2 of the work to determine its position and axis of rotation during formation of the race'ways. In this manner, the race ways and the bore will be accurately concentric one with the other, and either can be correctively reground or varied as desired wit-hout in any wise affecting their relative concentricity. This again has been'impossible in the past, where the exterior grinding has been performed with the work held-on chucks, mandrels, or other centering devices engaging the interior surface while the race was being formed.

In the carrying out of the process therefore the work is first suitably ground,.as for example, in a centerless grinder such' as diagrammatically indicated in Figure 6, to produce the truly cylindrical outer surface l2; The succeeding two steps of the process can then be alternatively performed, for example, first mounting the work as shown in Figures 7 and 8. In these figures use is preferably made of a supplemental pressure roller 22 to maintain proper two-point contact of the members 20 and 2| withthe periphery of the work 'the work is restrained against independent axial movement, there is preferably effected an axial movement relatively between the grinding wheel and its supporting unit, so that the grinding wheel properly traverses the inner surface of the work, producing a smooth finish thereon without grooves or scratches.

In the formation of the race way or race ways, the work is again supported, as indicated in Figures 9 and 10, on its outer periphery by engage- -ment of the members 20a and Zla therewith, and

While so held and rotated, it is exteriorally engaged, as by the grinding wheel 26 having a formed peripheral surface for production of the race way. This wheel may be mounted on a swivel support as at 21, whose axis extends parallel with a tangent to the surface of the work .piece at the point of engagement of wheel 26 therewith. Since the swivel support 21 has a predetermined position-relative to the base of the machine and in predetermined position relative to the regulating wheel 2|a', it is apparent that the grinding wheel 26 is mounted in predetermined relation to the outer surface of the workpiece and accordingly in predetermined relation to the axis of rotation of said workpiece, the axis of rotation being concentric to the cylindrical outer surface. With this arrangement the wheel may be oscillated about its axis properly, to generate by transverse oscillation the correct transverse curve in the individual peripheral race way. It will, of course, be understood that this generative action depends on a relative oscillation of the grinding wheel and work about the proper center, and if preferred'can be effected by a movement of the work and its supporting and driving unit, in place of the movement of the wheel, or in some instances the contour of the race way may be a direct contrageneric reproduction of the existing curve on the periphery of wheel 26.

From the foregoing, it will be apparent that the process involves the production of a multiplicity of concentric surfaces on a workpiece by simultaneously or successively grinding each of the concentric surfaces while the workpiece is supported and rotated on a preformed cylindrical surface. The latter.,maybe formed as the first step in the process when the workpiece in its unfinished form is not already provided with such a cylindrical surface. It will be apparent that the concentric surfaces may be cylindrical or conical, or the surfaces may extend radially as in finishing the parallel faces of the ball race shown, which surfaces, for' accurate positioning of the ball race on the spindle I5, must be concentric to the cylindrical surface I31; and the race ways l6 and H.

We claim:

1. The process of producing a tubular article having concentric inner and outer surfaces, consisting in first forming a true cylindrical exterior surface thereon, rotating the article on said preformedsurface while internally abrading same and effecting a relative axial translation between the work and abrading member to generate a true inner cylindrical bore, and similarly rotating the work piece on said preformed outer surface while restraining the same against axial movement, abrading a predetermined portion of said preformed outer surface to produce a groove or depression therein, whereby said in ner cylindrical surface and outer groove will be produced accurately concentric one to the other through use of the preformedouter surface as a position determinate during their formation.

2. The process of producing a tubular article having concentric inner and outer surfaces, consisting in first forming a true cylindrical exterior surface thereon, rotating the article on said preformed surface while internally abrading same and effecting a relative axial translation between the work and abrading "member to generate a true inner cylindrical'bore, and similarly rotating the work piece on said preformed outer surface while restraining the same against axial movement, abrading a predetermined portion of said preformed outer surface to produce a groove or depression therein, and effecting a relative oscillatory movement between the work piece and abrading member to generate the desired form of groove therein, whereby said inner cylindrical surface and outer groove will be produced accurately concentric one to the'other through use of the preformed outer surface as a position determinate during their formation.

3. The process of producing an accurate tubular article such as an inner ring or race for a ball bearing, consisting in initially forming the non-operative outer surface thereof to true cylindrical form by grinding in a centerless grinder, supporting the work on its periphery by a work rest between grinding and regulating wheels, subsequently supporting and rotating the work by a rest and regulating member engaging the preformed outer periphery, abrading the inner surface thereof by an abrading member operating in opposition to the work piece supports to produce an inner surface in concentric relation'to said preformed outer surface, similarly supporting and rotating the Work piece, restraining same against axial movement relative to its supports, abrading a selected portion of the outer periphery thereof during rotation, and effecting an oscillation between the work and its external abrading means to generate a peripheral groove on the work, whereby said groove and inner surface of the work will be formed independent one to the other, but concentric each with the other, through utilization of the preformed non-operative outer surface as the common position determinate for the work during generation of the subsequent surfaces.

CLEMENT BOOTH. SOL EINSTEIN. 

